🚬 Cigarette Smoke & Vaping May Cause Lasting Changes to Immunity and Blood Formation
A study published in Toxicological Sciences (DOI: 10.1093/toxsci/kfag096) reports that exposure to cigarette smoke and e-cigarette aerosol can affect immune cells and the body’s blood-forming system. The findings are concerning because some changes appeared to persist even after exposure stopped.
🔬 Key Findings
1. Cigarette smoke suppressed immune responses
In several laboratory macrophage models, cigarette smoke extract reduced TNF-α, an important inflammatory cytokine, after stimulation with lipopolysaccharide. This suggests cigarette smoke can interfere with aspects of the immune response.
2. Cigarette smoke promoted foam-cell formation
Smoke exposure increased lipid accumulation in macrophages, producing more foam cells, which are associated with an early stage of atherosclerosis.
The effect was reduced by N-acetylcysteine (NAC), suggesting that oxidative stress/reactive oxygen species may contribute to this process.
3. Both cigarette smoke and e-cigarette vapor affected blood-forming cells
In mouse bone-marrow experiments, both cigarette smoke extract and e-cigarette vapor extract reduced myeloid colony formation in a dose-dependent manner.
This indicates that components of both types of exposure can interfere with the ability of hematopoietic progenitor cells to proliferate or differentiate normally.
🩸 What Happened After Switching From Cigarettes to E-Cigarettes?
One particularly interesting part of the study involved mice exposed first to combustible cigarette smoke and then switched to e-cigarette aerosol.
The smoke-to-e-cigarette group developed:
- Increased platelet counts
- Greater production of myeloid cells
- Persistent changes in blood-cell output
When bone marrow from exposed animals was transplanted into unexposed mice, increased monocytes and macrophages were still observed over time. The smoke-to-e-cigarette group also showed reduced neutrophil frequency.
This suggests that some effects of smoke exposure may be durable within the hematopoietic system.
🧬 Possible Mechanism
The researchers observed a pattern resembling myeloid-biased hematopoiesis, which can occur with aging.
However, the study did not establish exactly why these changes persist. Possible explanations include:
- Epigenetic changes in hematopoietic stem cells
- Expansion of myeloid-biased stem-cell populations
- Changes occurring at the progenitor-cell level
More research is needed to distinguish between these possibilities.
⚠️ Important Limitation
The findings do not mean that vaping and smoking have identical effects.
For example, cigarette smoke consistently suppressed TNF-α in several experimental macrophage models, whereas the e-cigarette vapor extract alone had little effect on TNF-α in those experiments.
Also, the animal study did not include an e-cigarette-only exposure group, and the specific vaping products and exposure conditions used in the laboratory may not represent all commercially available products.
Human immune-cell results were also variable: among nine donors, six showed reduced TNF-α responses while three showed increased responses.
🧪 Bottom Line
The study provides experimental evidence that cigarette smoke can cause persistent alterations in immune and blood-forming systems, and that e-cigarette aerosol can also affect hematopoietic progenitor cells under the experimental conditions used.
Importantly, this was primarily a laboratory and animal study, so it does not establish that the same magnitude or persistence of effects occurs in humans. Long-term human studies are needed.
Reference: Toxicological Sciences, DOI 10.1093/toxsci/kfag096.
